camera stopped working

hello! i bought smasung galaxy S2 19100 i5 days ago but my camera has stopped working.if i click camera it shows a black out screen i can see camera setting buttons or front camera button but nothing responses and then suddenly phone takes me back to main menu page by giving a msg' UNFORTUNATELY CAMERA HAS STOPPED WORKING' please help me and tell me hoe to solve this proble.i have tried to restart it by switching on /off power button and taking out battereis and then restartig but nothing worked!help me please.